Presentation on theme: "Parvovirus B19 A negatively stained preparation of parvovirus seen by transmission electron microscope. www.wadsworth.org."— Presentation transcript:
Parvovirus B19 A negatively stained preparation of parvovirus seen by transmission electron microscope. www.wadsworth.org
Parvovirus B19 Family: Parvoviridae – Latin parvus means small ~20 nm in diameter – (0.02 µm) Single-stranded DNA virus Icosahedral capsid No envelope Only known human parvovirus X-ray crystallographic image of parvovirus
Body source & Transmission Replication in human cells restricted to erythroid progenitor cells – Adult bone marrow – Fetal liver Transmission by close contact – Airborne droplets – 50% of a household may become infected – 10-60% of students in school outbreaks
Environmental Habitat Wide distribution among warm-blooded animals B19 is only known HUMAN parvovirus
Pathogenicity Associated with: – Encephalitis, neuropathies, myocarditis, nephritis, systemic lupus erythematosus (SLE), Henoch- Schönlein purpura (HSP), and rheumatoid arthritis Henoch-Schönlein purpura (HSP) Note: this is usually caused by the measles
Fifth Disease Six separate childhood exanthems were defined from what was once called the “measles” (Early 20 th Century) 1 st Measles (rubeola) Morbillivirus 2 nd Scarlet fever ( Streptococcus pyogenes ) 3 rd Rubella (German measles) 4 th Atypical scarlet fever Duke Filatow's disease staph 5 th Erythema infectiosum 6 th Roseola herpesviruses (HHV-6 and HHV-7) Exanthem = rash Fifth disease is the only one still called by this name
Symptoms – Fifth Disease Incubation 7-10 days Lasts 5-7 days Three Phases – First phase –peak level of virus and RBC destruction Fever Malaise Chills Bright red, raised “slap cheek” rash
Symptoms – Fifth Disease Second phase – rash and arthralgia ○ Virus has disappeared – no longer infectious ○ Caused by immune complexes in the capillaries of the skin ○ Appears at presence of parvovirus IgM ○ Erythematous maculopapular rash on arms and trunk ○ Fades into a lace-like reticular pattern Third phase ○ Frequent clearing and recurrences for weeks ○ Due to stimuli such as exercise, irritation, or overheating of skin from bathing or sunlight.
Erythema infectiosum “Slap cheek” rash on the face, lacy rash on the extremities.
Symptoms – Aplastic Crisis Anemic patients Pallor, fatigue, drop in hemoglobin >1g/dL Destroys infected red blood cells No reticulocytes to replace aging or damaged erythrocytes This normally happens in disease but is symptomatic in anemic patients Thrombocytopenic patients Bruising Typical giant proerythroblast (arrow) seen in parvovirus B19-associated pure red cell aplasia with highly uncondensed chromatin and pale purple intranuclear inclusions. Bone marrow aspirate.
Symptoms – Hydrops Fetalis Pregnant women exposed to B19 should have IgG and IgM serology ASAP – Repeat serology tests in 3 weeks. Development of IgM indicates an acute infection. – Can be fatal to the fetus IgGIgMRisk PositiveNegativeNo risk Positive Possible risk NegativePositiveHigher risk Negative No infection
Hydrops Fetalis The fetus weighing 1,010 g shows features of hydrops fetalis. Mild maceration is observed
Hydrops Fetalis In the internal organs, the markedly anemic (pale yellowish brown-colored) liver is quite characteristic (gross findings). The fetus with hepatic hematopoiesis (19-29 weeks of gestation) is susceptible to this single-stranded DNA virus.
Identification Lab studies not normally done because it resolves in 5-7 days Serology – IgM and IgG – ELISA – Radioimmunoassay (RIA) – Immunofluorescence – Difficult to interpret Polymerase Chain Reaction (PCR) – Useful for clinical diagnosis – Detects viral DNA in serum Cannot be cultured in cells
Treatment Mainly supportive care Acetaminophen or Ibuprofen for fever Topical anesthetic or antihistamine for itching Intravenous Immunoglobulin (IVIG) in chronic parvovirus Aplastic crisis may require packed RBC transfusion Vaccine is in trials
Henoch-Schönlein purpura (HSP) This picture is for Natalie